Abstract

We report a prototype of high-speed real-time physical random bit generator based on a chaotic laser. The chaotic laser consists of a semiconductor laser with optical feedback in fiber external cavity configuration. The chaotic laser intensity signal is quantized into binary stream by differential comparison which makes the amplitude distribution symmetric with respect to zero mean value. An exclusive-OR gate operation between two raw binary streams from the chaotic signal and its delayed signal is used to overcome the influences of the weak periodicity induced by the external cavity resonance inherent in the chaotic laser. After exclusive-OR operation, the prototype can generate a single fast random bit stream in real time without any off-line processing procedures. Its bit rate can be handily and continuously tuned up to 4.5 Gbps by a trigger clock. Experiment results demonstrate that our generator possesses high-quality randomness with verified by the three-standard-deviation criterion and industry-benchmark statistical tests.

Characteristics of the calculated temporal waveform V(t)-V(t-τ) through doing subtraction between the measured chaotic signal V(t) and its delayed signal V(t-τ). (a) Time series and (b) its associated statistical histogram. The Pearson’s median skewness coefficient of the histogram is −0.001.

Photographs of the generated random bit stream after a XOR operation recorded by a real time oscilloscope (LeCroy SDA806Zi-A) when the CLK frequency is set to 4.5 GHz. (a) Temporal waveforms, where these units in vertical and horizontal axes are 200 mV/div and 5 ns/ div, respectively; (b) Eye diagram, where these units in vertical and horizontal axes are 200 mV/div and 37 ps/ div, respectively.

Typical results of NIST statistical tests. Using 1000 samples of 1 Mb data and significance level β = 0.01, for “Success”, the P-value (uniformity of p-values) should be larger than 0.0001 and the proportion should be greater than 0.9805608.